In recent years, with increasingly higher integration and densities of semiconductor devices, wires of circuits become increasingly finer and also the number of layers of multilayer interconnection is on the rise. To realize a multilayer interconnection while attempting to make wires of circuits finer, a step becomes ever larger by following surface unevenness of a lower layer and thus, with an increasing number of layers of interconnection, step coverage in thin film formation deteriorates. Therefore, to realize a multilayer interconnection, it is necessary to improve the step coverage and to carry out planarization in a proper process. In addition, the depth of focus becomes shallower with increasing fineness of optical lithography and it is necessary to planarize the surface of semiconductor devices such that an uneven step on the surface of semiconductor devices remains within the depth of focus. With increasing fineness of circuits, requirements for precision in planarization become higher. Also, with an ever more complex structure of a transistor periphery, precision requirements of planarization become higher not only in a multilayer interconnection process, but also in FEOL (Front End Of Line).
In a semiconductor device manufacturing process, therefore, planarization technologies of the surface of a semiconductor device become increasingly important. Among the planarization technologies, the most important technology is CMP (Chemical Mechanical Polishing). The chemical mechanical polishing polishes a substrate such as a semiconductor wafer by using a polishing device and bringing the substrate into sliding contact with a polishing surface while supplying a polishing liquid containing abrasive grains such as silica (SiO2) onto the polishing surface such as a polishing pad.
This kind of polishing device includes a polishing table having the polishing surface made of the polishing pad and a substrate holding device called top ring, a polishing head or the like to hold a semiconductor wafer. When a semiconductor wafer is polished by using such a polishing device, the semiconductor wafer is pressed against the polishing surface with a predetermined pressure while the semiconductor wafer being held by the substrate holding device. By relatively moving the polishing table and the substrate holding device, the semiconductor wafer is brought into sliding contact with the polishing surface and the surface of the semiconductor wafer is polished flatly like a mirror finished surface.
If, in such a polishing device, a relative pressing force between the semiconductor wafer being polished and the polishing surface of the polishing pad is not uniform over the entire surface of the semiconductor wafer, insufficient polishing or excessive polishing may occur in accordance with the pressing force given to each portion of the semiconductor wafer. To make the pressing force on the semiconductor wafer uniform, a pressure chamber formed of a membrane is provided in a lower portion of the substrate holding device and a fluid such as a pressurized air is supplied into the pressure chamber so that polishing is performed while the semiconductor wafer being pressed against the polishing surface of the polishing pad by a fluid pressure via the membrane.
On the other hand, a thin film formed on the surface of a semiconductor wafer to be polished has a different thickness from position to position in the radial direction of the semiconductor wafer depending on the method of forming the thin film and device properties. That is, the surface of a semiconductor wafer has an initial thickness distribution in the radial direction. The above substrate holding device that uniformly presses and polishes the entire surface of the semiconductor wafer uniformly polishes the entire surface semiconductor wafer and thus cannot correct the initial thickness distribution of the surface of the semiconductor wafer.
Thus, a polishing device that controls the pressure of a fluid such as a pressurized air supplied to each of a plurality of pressure chambers formed from a membrane in a plane of a semiconductor wafer is proposed (for example, JP 2006-128582 A). This polishing device partially controls the pressure applied to the semiconductor wafer such that a pressing force on the polishing surface of a thick portion becomes larger than that of a thin portion to selectively increase the polishing rate of such a portion, thereby enabling flat polishing of proper thickness over the entire surface of the substrate without depending on the thickness distribution when the film is formed.
An object of the present technology is to provide a polishing device and a polishing method capable of polishing an object to be polished with precision.
According to an embodiment, provided is a polishing device that polishes a surface to be polished of an object to be polished by relatively sliding the surface to be polished and a polishing member including a pressing unit that presses the surface to be polished against the polishing member by pressing a back side of the surface to be polished of the object to be polished, a thickness measuring unit that estimates a remaining film profile of the surface to be polished of the object to be polished during polishing of the object to be polished, and a control unit that controls a pressing force on the back side of the surface to be polished by the pressing unit in accordance with a measurement result by the thickness measuring unit during the polishing of the object to be polished, wherein the control unit controls not only the pressing by the pressing unit during the polishing of the object to be polished, but also a periphery of the pressing unit affecting a pressing force of the surface to be polished on the polishing member during the polishing.
With this configuration, the pressing of the surface to be polished of a portion pressed directly by the pressing unit against the polishing member is controlled not only by the control of the pressing by the pressing unit, but also by the control of the pressing of the surface to be polished of the portion by the periphery against the polishing member and therefore, highly precise polishing can be performed. In addition, such control is exercised in accordance with polishing conditions during polishing of the object to be polished and even if a pressing force by the pressing unit is changed during the process of polishing, the periphery can be controlled accordingly.
In the polishing device, the periphery may be a retainer member that presses the polishing member near the pressing unit and the control unit may control not only the pressing force on the back side of the surface to be polished by the pressing unit, but also a pressing force on the polishing member by the retainer member.
With this configuration, by controlling the pressing of the retainer member against the polishing member, the pressing of the surface to be polished of the portion directly pressed by the pressing unit against the polishing member is controlled and therefore, highly precise polishing can be performed.
In the polishing device, the pressing unit may press an edge region on the back side of the surface to be polished of the object to be polished and the retainer member may be a member surrounding the object to be polished.
With this configuration, by controlling the pressing of the retainer member against the polishing member, the pressing of an edge region of the surface to be polished whose back side is directly pressed by the pressing unit against the polishing member is controlled and therefore, highly precise polishing can be performed in the edge region.
The polishing device may include a plurality of the pressing units that partially presses the back side of the surface to be polished of the object to be polished and the periphery may be the other neighboring pressing unit.
With this configuration, the pressing of the surface to be polished of the portion whose back side is directly pressed by some pressing unit against the polishing member is controlled by controlling the pressing of the back side of the surface to be polished by another neighboring pressing unit and therefore, highly precise polishing can be performed.
In the polishing device, the periphery may be a mechanism that controls the pressing force of the surface to be polished by deformation of an elastic body of the pressing unit.
With this configuration, the pressing force of the surface to be polished by deformation of the elastic body of the pressing unit can be controlled based on polishing conditions.
In the polishing device, the periphery may be a mechanism that controls deformation of an elastic body of the pressing unit.
With this configuration, the deformation of the elastic body of the pressing unit can be controlled based on polishing conditions.
In the polishing device, the control unit may control a pressing force of the periphery such that a thickness profile of the surface to be polished becomes uniform or a desired shape over an entire surface of the surface to be polished whose back side is directly pressed by the pressing unit.
With this configuration, even if the influence from the periphery on the pressing of the surface to be polished whose back side is directly pressed by the pressing unit against the polishing member is not uniform on the surface to be polished whose back side is directly pressed by the pressing unit, the surface to be polished whose back side is directly pressed by the pressing unit can uniformly be polished.
In the polishing device, control limiting values may be set to control of the periphery and the control unit may control the periphery within a range of the control limiting values.
With this configuration, when the control unit exercises control according to a predetermined algorithm, the periphery can be prevented from being controlled beyond control limits and therefore, accidents such as damage to the object to be polished or the polishing device can be prevented.
In the polishing device, the pressing unit may be formed from a circular pressure chamber and a plurality of annular pressure chambers therearound.
With this configuration, the thickness profile in the radial direction can be made a desired shape.
According to an embodiment, provided is a polishing method for polishing a surface to be polished of an object to be polished by relatively sliding the surface to be polished and a polishing member, including a pressing process of pressing the surface to be polished against the polishing member by pressing a back side of the surface to be polished of the object to be polished by a pressing unit, a thickness measuring process of estimating a remaining film profile of the surface to be polished of the object to be polished during polishing of the object to be polished, and a control process of controlling a pressing force on the back side of the surface to be polished by the pressing unit in accordance with a measurement result in the thickness measuring process during the polishing of the object to be polished, wherein the control process controls not only the pressing force on the back side of the surface to be polished by the pressing unit, but also a periphery of the pressing unit affecting a pressing force of the surface to be polished on the polishing member during the polishing.
Also with this configuration, the pressing of the surface to be polished of a portion pressed directly by the pressing unit against the polishing member is controlled not only by the control of the pressing by the pressing unit, but also by the control of the pressing of the surface to be polished of the portion by the periphery against the polishing member and therefore, highly precise polishing can be performed. In addition, such control is exercised in accordance with polishing conditions during polishing of the object to be polished and even if a pressing force by the pressing unit is changed during the process of polishing, the periphery can be controlled accordingly.
In the polishing method, a pressing force of the periphery maybe calculated during the polishing using a relationship of the pressing unit and the periphery with a polishing speed of the surface to be polished whose back side is directly pressed by the pressing unit.
With this configuration, the control of the pressing unit and the periphery in accordance with a measurement result in the thickness measuring process can be exercised.
In the polishing method, the pressing force on the back side of the surface to be polished and the pressing force of the periphery may be determined simultaneously by closed loop control.
With this configuration, more precise control can be realized.